Generally, a stereo image display system achieves a stereo display effect by providing two sets of images that a left eye and a right eye of a viewer perceives in a time-interleaved manner. That is, when an image to be provided to the left eye of the viewer is displayed on a screen, only the left eye of the viewer can see the image; when an image to be provided to the right eye of the viewer is displayed on the screen, only the right eye of the viewer can see the image. To achieve the stereo effect in the prior art, left-eye and right-eye image frames are respectively alternately displayed in different timing intervals.
FIG. 1 shows a schematic diagram of timing of a control signal of a conventional stereo image display system. An image frame update signal (i.e., an interval signal) frm_u represents an updating cycle of different groups of image frames, e.g., during an interval between a time point T0 and a time point T1, the image frame update signal is maintained at a logical high level to update a right-eye image frame. At the time point T1, the right-eye image frame update ends, and the interval signal frm_u turns to a low level representing a logical low state. When the interval signal enters the logical low state, it means that the image signal enters an image vertical blanking interval (VBI) during which an updated right-eye image frame is completely displayed on the screen. The VBI lasts to the time point T2 from when the interval signal frm_u changes to a high level, so that the left-eye image frame begins updating to enter a left-eye image frame updating interval. Likewise, the left-eye image frame update lasts to time point T3 after which another VBI begins.
It is necessary for a viewer to wear a pair of 3D glasses to perceive the accurate stereo images by displaying left-eye and right-eye images in sequence by the stereo display system. Referring to FIG. 1, when the right-eye image frame is already updated and displayed on the screen during the VBI, a right-eye shield of the pair of 3D stereo glasses worn by the viewer is turned off, so that the right eye of the viewer is not shielded and the viewer can view the updated right-eye image frame. Likewise, when the left-eye image frame update is finished and the left-eye image frame is displayed on the screen during another VBI, a left-eye shield of the pair of 3D stereo glasses worn by the viewer is turned off, so that the left eye of viewer can view the updated left-eye image frame. Accordingly, the left eye and the right eye of the viewer can respectively view the updated left-eye and right-eye images during different timing intervals.
However, during the updating interval of the right-eye (or left-eye) image frame, the right-eye (or left-eye) image frame is being updated, if the right-eye (or left-eye) image frame is displayed during this time, the right-eye image frame shown is not a complete frame. Because a backlight module of a conventional display device is always turned on (backlight control signal bl_c shown in FIG. 1), the incomplete images are displayed on the screen. Therefore, in the prior art, during the right-eye (or left-eye) image frame updating interval, the left-eye shield and the right-eye shield of the pair of 3D stereo glasses are simultaneously turned on (i.e., shielding) to avoid viewing any incomplete right-eye or left-eye images that are being updated.
In other words, the left-eye shield and the right-eye shield of the pair of 3D stereo glasses worn by the viewer are turned off (shielding is off) only during VBIs to receive images displayed; however, light received by the viewer is very limited due to the short viewing time (because VBI is relatively short). The duty cycle of the VBI of the conventional stereo image display system is usually 30%, which also means that light-emitting efficiency of the display system is likewise only 30%.
Furthermore, in order to configure with the conventional stereo image display system as shown in FIG. 1, a control signal e_ctrl having a highly complex voltage triggering mechanism is needed to enable accurate turn-offs or turn-ons of the right-eye shield and the left-eye shield of the pair of 3D stereo glasses, which causes the stereo image display system to be of high hardware or software complexity.
Therefore, an advanced control to the backlight module of the 3D stereo image system is desired so that the backlight module can provide light source in different timing intervals (i.e., emitting or not emitting lights, and providing or not providing a light source to the displayer).